A method and a system for preventing annoying abrupt load-change jerks in an internal combustion engine for a motor vehicle are discussed in DE 37 38 719 A1. Such abrupt load-change jerks arise in particular in response to a sudden change in a setpoint torque of the internal combustion engine, which occurs when a driver suddenly activates or releases the accelerator pedal of the motor vehicle, for example. If such an abrupt change of the setpoint torque is converted directly into a corresponding sudden change of an actuating variable of the internal combustion engine, then a load-change jerk will often occur, which the driver perceives as annoying and which is followed by load change oscillations.
According to the present method, a delayed conversion of an abrupt change for the setpoint torque specified by the accelerator into a change in the actuating variable is implemented at the exact moment when a torque characteristic of the internal combustion engine is passing through zero. This achieves a relatively soft transition from an acceleration operation of the internal combustion engine in which the torque of the internal combustion engine is positive (the internal combustion engine is driving the motor vehicle), into trailing throttle operation of the internal combustion engine in which the torque is negative (the internal combustion engine is braking the motor vehicle), as a result of which the load-change jerk is able to be avoided and the subsequent load-change oscillations are reduced or, ideally, avoided completely. In a corresponding manner, the load-change jerk and the load-change oscillations that occur in a transition from acceleration operation to trailing throttle operation of the internal combustion engine are reduced or avoided. Methods that reduce or eliminate the toad-change jerk and/or the load-change oscillations are generally often referred to as method for load-change formation.
Since motor vehicles are usually not equipped with sensors for ascertaining the torque of the internal combustion engine, it is necessary to determine the torque from various state variables, often with the aid of a characteristics map. However, in the region of the zero crossing, especially in the region of the zero crossing of the torque characteristic, a precise determination of the torque is impossible; as a result, there is the risk that a time interval during which the torque of the internal combustion engine is in the region of the torque's zero crossing is ascertained incorrectly, and the implementation of the abrupt change of the setpoint torque into the change in the actuating variable takes place in delayed fashion not in the region of the torque's zero crossing but in a different region of the torque characteristic. This limits the effectiveness of the method.